What was found
GOT CABIN SMOKE LVL 3 AND ASSOCIATED TONE ON CLIMB-OUT. LIGHT STAYED ON ABOUT 5 MINUTES. NR 7 SMOKE DETECTOR ILLUMINATED AT SAME TIME. DECLARED EMERGENCY AND RETURNED TO MEM. CREW STATED AT GATE THAT THEY HAD NO SMOKE INDICATION LIGHT ON OVERHEAD CARGO FIRE TEST PANEL. ONLY THE NR 7 SMOKE DETECTOR WAS ILLUMINATED. DEPINNED PLUGS AND INSP CRIMPS, CK'D GOOD. ALSO CK'D CONTINUITY OF ASSOC WIRING FROM MSC TO SMOKE DET'S NR 7 AND NR 9 (REF WDM 26-15-01 AND 26-14-02), ALL CK'D GOOD. OHMED DIODES R7-570 AND R7-572, BOTH CK'D GOOD. FOUND LOOSE SCREW INSIDE NR 7 SMOKE DET LAYING ON CIRCUIT CARD, COULD BE POSSIBLE CAUSE OF FAULT.